Art of promoting crystal growth



United States Patent ART (BF PROMOTING CRYSTAL GRUWTH Penn F. dpitzer, In, South Bound Brook, and @scar L. Burgenson, In, New Market, N1, assignors to American Cyanarnid Company, New York, 'N.Y., a corporationlof -Maine No Drawing. Filed Aug. 24, 1960, Ser. No. 51,493

- t lit-Claims. (Cl. 260-256.4)

wherein R represents a member of the group consisting "of aliphatic and alicyclic radicals containing at least 7 carbon atoms, R and R" each represent a member of the group consisting of alkyl and hydroxyalkyl radicals containing from 1 to carbon atoms, inclusive, R

represents a member of the group consisting of alkyl,

. hydroxyalkyl, alkenyl and aralkyl radicals, and Y represents an anion.

Illustrative examples of radicals represented by R in Formula I are heptyl, octyl, octenyl, nonyl, nonenyl, decyl, decenyl, undecyl, undecenyl, tridecyl, vtetradecyl, tetradecenyl, heptadecyl, heptadecenyl, octa'decyl, octadecenyl, the residueof abietic acid, etc. Illustrative examples of radicals represented by R and R are methyl, ethyl, propyl, isopropyl, n-butyl, isobu-tyl, sec.-butyl, .tert -butyl, n -amyl, isoarnyl, sec.-amyl, tert.-amyl and the other isomeric amyl radicals,'hyd-roxyethyl, hydroxypropyl, hydroxyisopropyl, dihydroxypropyl, hydroxybutyl, dihyd-noxybutyl, hydroxyamyl, dihydroxyamyl, etc. Illustrative examples of radicals represented by R are the same alkyl and hydroxyalkyl radicals as those given with reference to R and R and, in addition, the higher alkyl radicals, e.g., hexyl to oct-adecyl, inclusive, the mono-, di-, triand higher hydroxy derivatives of the aforementioned higher alkyl radicals (i.e., hexyl to octadecyl, inclusive); the same alkenyl radicals as those given above with reference toR and, also, allyl, methallyl, ethallyl, Z-butenyl, S-b-uteny, 3-methyl+2-butenyl, 3-pentenyl, 4-pentenyl, 2,3-penitadienyl, 3-methyl-3-butenyl and the higher alkenyl radicals, e.g., hexenyl to octadecenyl, inclusive; and the various aralkyl radicals, e.g., benzyl, phenylethyl, phenylpropyl, phenylisopropyl, phenylbutyl, etc. Illustrative examples of anions represented by Y are the halide ions (that is, Y can represent a chloride, bromide, fluoride or iodide), sulfate, sulfonate, phosphate (more particularly dihydrogen phosphate), hydroxide, borate, cyanide, carbonate, hydrocarbonate, thiocyanate, isocyanate, sulfite, bisulfite, nitrate, nitrite, oxalate, silicate, sulfide, cyanate, acetate and the other common inorganic and organic anions.

Quaternary ammonium compounds of the kind used in practicing the present invention are disclosed in, for instance, Cannes US. Patents 2,626,876 and 2,626,877. Reference also is made to Cook et al. US. Patent 2,- 589,674 which discloses how compounds used in prac ticing this invention can be prepared, and wherein are claimed a sub-class and certain species of quaternary ammonium compounds that are useful carrying the present invention into eifect.

A more specific embodiment of the present invention a is the improvement, in the removal by filtration of finelydivided particles of organic material from an aqueous sus- Y Patented Apr. 2?, 1965 prises adding to a solution, containing a crystallizab-le organic material capable ct crystallizing from said solution, at least about 0.1% (cg, from 0.1 to 10% or more) by weight, based on the dry Weight of the said crystallizable organic material, of a crystal-growth pro moter comprising or consisting essentially of a quaternary ammoniurn compound of the kind embraced by Formula I. The upper limit of the amount of the quaternary ammonium compound employed is not critical. It may be, by Weight, about 0.2%, or 0.5%, or 1%, or

as much as about 2 or 3% or even 5% or 10% or more, based on the :dry weight of the crystallizable organic material. No advantages appear to accrue from the use of more of the quaternary ammonium compound than is necessary to provide the desired crystal growth and the accompanying improvement in filterability of the aqueous suspension ofthe particles or crystals of organic material, as wellas the other advantages hereinafter set forth. The use of any excess of the defined crystal-growth promoter above that needed to secure the desired results seems to be wastedand only adds to the cost of the process.

In industrial chemical operations it is ofiten necessary to filter solid suspended material from aqueous suspen sions. When particles are very finely divided, difficulty is often encountered in such filtration. In some instances, particles are so finely divided that they pass through the filtering medium; or, the size of the particles may be i such that the filtering cloth or other medium becomes plugged, thereby reducing the rate of filtration so that excessive time is required for this operation; or, filtra tion may not be carried out completely, resulting in a very wet or sloppy filter cake. Further difiiculties may be caused, in addition to loss of material and slow fiitra tion, in that processing of the sloppy or mushy filter cakes maybe extremely diilicult and more costly.

The present invention is based on our discovery that, by adding .a cationic quaternary ammonium compound of the kind embraced by Formula I to a liquid mas or solution (more particularly an aqueou liquid mass or solution) containing a crystallizable organic material or compound, crystal growth surprisingly is promoted. Consequently, in subsequent filtration operations filtration is improved, and difficulties arising from loss of material, excessive filtering periods and sloppy or mushy filter .cakes are avoided.

It was most surprising and unexpected that compounds of the kind embraced by Formula I should be capable of acting as crystal-growth promoters and should provide such excellent and non-obvious results. Such effects are e not obtained generally with surface-active agents of various types includingcationic, anionic and nonionic agents. To the best of our knowledge and belief the improvement is specific with respect to the be expected and in no way could have been predicted that, bythe use of an agent which has dispersant properties, crystal growth of a crystallizable organic material would be promoted and in consequence of which the improved filtration effects herein described would result.

The present invention should not be confused with any prior suggestions of the use of a compound embraced by Formula I as a settling agent that is applied to various insoluble slimes, including bacterial suspensions as .well as chemical and mineral substances, and

wherein the addition of as little as parts per million of the quaternary ammonium compound may cause rapid settling of the suspended substance. To the best of our knowledge and belief such suggested use of the quaternary ammonium compounds embraced by Formula I as settling agents was not applied to, and was not known to be applicable to, crystallizable (or potentially crystallizable) organic materials of the kind with which this invention is concerned. As is well known to those skilled in the art, a suggestion of settling a particular organic material is entirely different from a teaching of imparting crystal-growth characteristics to a crystallizable (or potentially crystallizable) organic material, and a teaching or a suggestion with respect to the one is in no sense of the word a teaching or a suggestion with respect to the other.

Illustrative examples of organic materials, more particularly crystallizable (including potentially crystallizable) organic materials, that can be modified in accordance with this invention to promote their crystal growth and thereby improve the filterability of aqueous suspensions or slurries of the thusly modified organic material are:

Z-aminodiazine bisulfite Ferrous calcium citrate Acetylsulfanilyl chloride Other examples of crystallizable and potentially crystallizable organic materials to which the present invention is applicable will be apparent to those skilled in the art from the foregoing illustrative examples.

The invention may be illustrated by the method and results obtained in the use of compounds of the kind embraced by Formula I in the manufacture of 2-amino- 1,3-diazine bisulfite, which is the bisulfite product of 2- aminopyrimidine and hereafter is designated for brevity as 2-aminodiazine bisulfite or, merely, as aminodiazine bisulfite. The compound is an intermediate in the manufacture of Z-aminodiazine (2-aminopyrimidine), which is an intermediate for making sulfadiazine, a well-known sulfa drug.

This process involves the filtration of a suspension of aminodiazine bisulfite. Under ordinary circumstances this filtration step is extremely difiicult, requiring excessive periods of time with loss of material and involving sloppy and mushy filter cakes, which are difficult to wash and costly to process.

In practical plant operation of a process for making 2-aminodiazine (hereafter for brevity sometimes designated as aminodiazine), the 2-aminodiazine reaction mixture is drowned in water. The Z-aminodiazine, prepared in any convenient manner, is isolated from the drowned reaction mixture containing process salts, unused reactants, by-product material, etc., by first neutralizing the aqueous solution with ammonia followed by treatment of this solution with sulfur dioxide, which causes precipitation of 2-aminodiazine bisulfite. This aqueous suspension is subjected to filtration, giving a filter cake of aminodiazine bisulfite. To isolate Z-aminodiazine, this bisulfite compound is treated with concentrated aqueous ammonia thereby to obtain, at 60 C., a solution of 2-aminodiazine. The Z-aminodiazine is crystallized from this solution by cooling and is removed by filtration, thus isolating the desired solid 2-aminodiazine.

The mother liquor from this Z-aminodiazine filtration contains a substantial amount (e.g., from about 10 to by weight of the total end-product) of 2-arninodiazine, and excess ammonia in aqueous solution. The solution also contains ammonium sulfite. To recover the Z-aminodiazine from this mother liquor, the mother liquor containing dissolved Z-aminodiazine is acidified with a mineral acid, e.g., HCl, H 80 etc. Ordinarily plant by-product mineral acid is used, for instance acid mother liquor from the precipitation of acetylsulfanilyl chloride containing sulfuric and hydrochloric acids.

This acidification liberates S0 which, in turn, converts the Z-aminodiazine in the reaction mass to Z-aminodiazine bisulfite. This mixture is then filtered to recover the Z-aminodiazine bisulfite. This may be filtered as such or generally, in commercial practice, along with a fresh batch of aminodiazine bisulfite. It is this filtration of Z-aminodiazine bisulfite either alone or in combination with the fresh aminodiazine bisulfite where extreme difficulty is encountered, e.g., loss of material, long filtration periods, sloppy filter cakes, etc. In addition, it frequently happens that acidification of aminodiazine mother liquor results in suspensions wherein the solid is so fine that the milky suspension passes completely through the filter cloth and the filter paper, resulting in a total loss of recoverable product amounting to from about 10 to 15% of the total weight of product that should be obtained.

By the addition of at least 0.1% and preferably from 0.2 to 1.5% by weight of a quaternary ammonium compound of the kind embraced by Formula I to the Z-aminodiazine mother liquor before acidification, which weight is based on the dry weight of the aminodiazine present therein, the filterability of the suspension containing the crystalline 2-aminodiazine bisulfite is improved due to its larger particle size; the yield of recovered Z-aminodiazine bisulfite is increased; and the aforementioned difliculties are obviated. The quaternary ammonium compound employed in practicing the present invention is usually added as the commercially available 50% solution in an isopropyl alcohol-water mixture.

In order that those skilled in the art may better understand how the present invention can be carried into effect, the following examples are given by way of illustration and not by way of limitation. All parts and percentages are by weight unless otherwise stated.

EXAMPLE 1 The procedure for the preparation of Z-arninodiazine bisulfite and conversion to Z-aminodiazine as described above may be outlined as follows:

Solution of 2-aminodiazine (60 0.)

Cool and crystallize (5 C.) Filter Solid Mother liquorcontains 10-15% of the 2-amino- Z-ammodlaztne diazine in solution. Contains also ammonium sulfite in solution Acidity with mineral acid liberated) Solid Z-aminodiazine bisulfite Filter (as such, or usually along with a fresh batch of aminodiazine bisulfite) (A) When the procedure is carried out as outlined,

(1) The filtration time for filtration of the aminodiazine bisulfite in a batch size for about 635 lbs. of aminodiazine varies from about 4 to 16 hours;

(2) An amount in excess of 30-35 lbs. of aminodiazine bisulfite per batch is lost (occasionally as high as 60-70 lbs);

(3) A sloppy filter cake of 2-aminodiazine bisulfite, consistency of about thick pea soup with considerably retained acid liquor, is obtained; and

(4) The retention of large amounts of acidic mother liquor in the sloppy cake requires excessive aqua ammonia usage in converting to aminodiazine with resultant increase in batch volume, decreasing aminodiazine isolated because of solubility in larger volume of liquor, increase in recovery and recycling problems, and cost increases due to losses, additional raw materials-and labor.

(B) When about 3-5 lbs. of a 50% solution in a 50-50 fl-hydroxyethyl ammonium nitrate is added to the aminodiazine mother liquor (containing 60-90 lbs. of aminodiazine in a total of 3500 lbs. of total solution), improved results are obtained as follows:

(1) The filtration time of the aminodiazine bisulfite is reduced from about 4 to 16 hours per batch to less than 1 hour per batch.

(2) There is a minimum improvement in the yield of aminodiazine of 30-35 lbs. per batch (batch size average about 635 lbs), and the elimination of the occasional 60-70 lb. losses.

(3) There is obtained a dry, sandy filter'cake of aminodiazine bisulfite having very little retained moisture. It is readily handled, thereby reducing labor costs, and is capable of complete washing without any difficulty.

There is no retention of acid solution and it may be converted to aminodiazine with improved results, e.g., reduced ammonia usage, due to less retaining acid, lower volume, etc.

By the improved method, there is obtained a coarse, harder crystal of aminodiazine bisulfite which filters rapidly, gives a dry cake with little loss of material.

Instead of using stearamidopropyl dimethyl B-hydroxyethyl ammonium nitrate, the formula for which is II as described under B of Example 1, essentially the same 7 results are obtained by employing an equivalent amount of any other compound (or mixture of compounds) em-.

braced by Formula I, specifically one or more of the following:

A caprylamidopropyl dimethyl beta-hydroxyethyl ammonium salt, e.g., chloride,,nitrate, sulfate, phosphate (dihydrogen phosphate).

A stearamidopropyl dimethyl dihydroxypropyl ammonium salt, e.g., chloride, nitrate, sulfate, phosphate.

A stearamidopropyl tris(beta-hydroxyethyl) ammonium salt, e.g., chloride, nitrate, sulfate, phosphate.

A lauramidopropyl methyl bis (beta-hydroxyethyl) ammonium salt, e.g., chloride, nitrate, sulfate, phosphate.

An abietamidopropyl dimethyl (beta-hydroxyethyl) ammonium salt, e.g., chloride, nitrate, sulfate, phosphate.

A steararnidopropyl dimethyl benzyl ammonium salt, e.g.,

chloride, nitrate, sulfate, phosphate.

A myristamidopropyl dimethyl benzyl ammonium salt,

e.g., chloride, nitrate, sulfate, phosphate.

A caprylamidopropyl dimethyl benzyl ammonium salt,

e.g., chloride, nitrate, sulfate, phosphate.

A stearamidopropyl trimethyl ammonium salt, e.g., chloride, nitrate, sulfate, phosphate.

A myristamidopropyl trimethyl ammonium salt, e.g., chloride, nitrate, sulfate, phosphate.

A palmitamidopropyl trimethyl ammonium salt, e.g., chloride, nitrate, sulfate, phosphate.

Also, the quaternary ammonium compounds identified by their formulas in column 4, lines .3 to 68, inclusive (Formulas IV through XVI) of the aforementioned Carnes US. Patent 2,626,877.

6 EXAMPLE 2.-.PREPARATION 0F FERROUS CAL- CIUM CITRATE (A) Under an inert atmosphere, e.g., gaseous nitrogen, 700 parts of water is mixed with parts calcium carbonate, 11.6 parts powdered iron, and 3 parts concentrated hydrochloric acid. To the mixture is then added 153.7 parts citric acid, after which it is stirred at 100l02 C. for 6 hours. After cooling to 25 C. the

product, ferrous calcium citrate,.is isolated ,byfiltration,

Washed and dried.

The filtration proceeds slowly and materially increases the cost of the process. Also, the product dries with difficulty to very fine crystals with poor flow qualities.

(B) The same procedure is followed as described under (A) with the exception that, inone case, one part of stearamidopropyl dimethyl p-hydroxyethyl ammonium phosphate (dihydrogen phosphate) and, in another instance, one part of. stearamidopropyl dimethyl ,B-hydroxyethyl ammonium nitrate is added to the reaction mixture before heating the same.

In both cases, and unlike the results obtained in the absence of the quaternary ammonium compound, the resulting product can be filtered rapidly from the reac tion mass. Furthermore, the washed product yields, after drying, large granular crystals with free-flowing characteristics.

Similar results are obtained when the corresponding sulfate or chloride is used in place of the particular quaternary ammonium salts used in the (B) portion of this example.

If desired, one can effectively use any other quaternary ammonium compound of the kind embraced by Formula I instead of the aforementioned stearamidopropyl dimethyl B-hydroxyethyl ammonium compounds.

EXAMPLE 3.ISOLATION OF ACETYLSULFANIL- YL CHLORIDE When acetylsulfanilyl chloride is isolated from suspensions thereof by filtration there are obtained, using the prior techniques, very fine particles averaging less than 1 to 2 microns and with only a relatively few agglomerates averaging as large as 15 microns. However, when the product before isolation is crystallized from a liquid medium or mass containing about 0.5% of stearamidopropyl dimethyl fl-hydroxyethyl ammonium phosphate or nitrate, the particle size is increased and a coarse, granular material ranging from 100 to 2400 microns in size is obtained. Most of the particles, in number, are in the range of 100 to 600 microns; while most of the particles by weight are in the range of 600 to 2000 microns.

When surface-active agents different from those used in practicing this invention, more particularly surfactants identified opposite Nos. 1 through 19 of Table II of Example 4, the above-described improvement in crystal size is not obtained.

EXAMPLE 4 A study was carried out to ascertain the influence of various types of surfactants upon crystal formation and filtration effects. For this purpose, the mother liquor from the filtration of aminodiazine was used (see Example l).

A large sample of the aforementioned mother liquor from a plant operation was divided into 400-part aliquots. To each aliquot was added 2 parts of surfactant. In the case of the stearamidopropyl dimethyl fi-hydroxyethyl diazine bisulfite was then removed by filtration. The time for filtration was noted and the product was dried and Weighed. g The results with various agents, including the aforementioned quaternary ammonium salts, are shown in Table I. This table shows the yield of material obtained in grams and, also, the filtration rate. In addition, Table I includes measurements to show the crystal growth results with reference to particle size.

It is to be noted that greatly improved results are We claim:

1. The method of promoting crystal growth of a crystallizable organic material selected from the group consisting of 2-aminopyrimidine bisulfite, ferrous calcium citrate and acetylsulfanilyl chloride, said method comprising adding to a liquid mass containing said organic material at least about 0.1% by weight, based on the dry weight of the said organic material, of a crystalgrowth promoter comprising a quaternary ammonium compound of the formula obtained by uslng quaternary ammonium salts or the kind embraced by Formula I (Nos. 20, 21 and 22 in the RCONHCHCH -CH NR" Y- tables). The filtration rate with these agents is from 1 2 2 T- to 2 minutes, whereas with the other agents much longer times are required- In addition, the amount of aminO- wherein R is a substituent selected from the group condiazine bisulfite obtamed from an aliquot portion is much sisting of abietyl and aliphatic hydrocarbon having from greater, generally p g, With the aforemfintionfid C 7 to 18 carbon atoms, inclusive, and wherein any unpounds than with any of the other agents. When s11rsaturation between adjacent carbon atoms is a double factant No. 7 was used, the amount of material isolated bond; R and R" each is a substituent selected from the was relatively high, but the slow filtration rate with this group consisting of unsubstituted alkyl having from 1 to surfactant would make it unsuitable for use. In a num- 5 carbon atoms, inclusive, and hydroXy-substituted alkyl ber of instances, the crystal size was improved as with having from 1 to 5 carbon atoms, inclusive, and which is surfactant No. 2 but the yield and filtration rates were otherwise unsubstituted; R' is a substituent selected unsatisfactory. from the group consisting of unsubstituted alkyl having Table II identifies the surfactants studied by their from 1 to 18 carbon atoms, inclusive, hydroxy-substituted chemical names and, also, by their ionic characteristics. alkyl having from 1 to 18 carbon atoms, inclusive, and

Table I Yield, Filter Range, Most No., Most Surfactant Grams lgiate, p. u wt., 1 Filter Cake Quality 1. 2 6-7 1-130 1-10 20-30 Sticky and gummy. 5.5 4 10-600 10-100 100-000 Granular, fairly dry. 3. 2 6 1-200 1-10 -200 Dense hard cake. 5.6 4 10-150 10-80 80-150 Granular fairly dry. 8. 2 5-0 2-300 2-50 -300 Fine particle, hard cake. 5. 9 5-6 1-350 1-l00 100-350 Soft crystals, hard cake. 8. 4 6-7 1-150 1-S0 80-150 Very fine particle, hard cake. 4.5 8 Sticky mass. 5. 2 6-7 1-200 1-60 60-200 Fine particle, hard cake. 5. 0 7-8 Sticky mass, soft crystals. 2. 6 4-5 1-80 1-5 5-80 Hard, dense cake. 6.1 4-5 10-150 10-80 80-150 Slightly granular, hard cake. 2. 6 4-5 1-40 1-5 5-40 Very fine particle. 4. 5 8 1-150 l-5 20-150 Sticky, discolored cake. 4. 9 6-7 l-l00 1-2 10-100 Fine particle, hard cake. 5. 4 5-0 1-100 1-2 20-160 Slightly granular, hard cake. 4. 4 8 1-200 1-2 20-200 Slightly granular, soft, sticky,

discolored. 0 Could not filter Soft, sticky mass. 4. 9 8 1-200 1-2 20-200 Fine particle, sticky. 8.6 1-2 5-400 30-100 100-400 Granular, dry, free flowing. s. 4 1-2 5-350 5-100 100-350 Do. 8. 3 1-2 5-350 5-100 100-350 Do.

1 Norm-Quaternary ammonium compounds of the kind embraced by Formula I.

Table II Surfactant Chemical Class Alkyl aryl polyether alcohol Nonionic. Tertiary amines; ethylene oxide condensates Cationic.

with primary fatty amines. Sodium alkyl sulfate Anionic. Tertiary amines; ethylene oxide condensates Cationic.

with primary fatty amines. Polyoxyethylene sorbitan monolauratc Nonionic. Sorbitan monolaurate D o. Ethylene oxide condensate with condensate D0.

of propylene oxide and propylene glycol. Sulfated and sulfonated fatty acid esters in Anionic.

mixture with aliphatic hydrocarbons. Fatty alcohol amine sulfate Do. Polyoxyethylene-iatty compound conden- Nonionic.

s e. Ethylene oxide condensate with condensate D0.

of propylene oxide and propylene glycol. Pyridiniurn chloride Cationic. Allryl aryl polyethylene glycol other- Nonionic. Dioctyl ester of sodium sulfosuccinic acid- Anionic. Alkyl aryl ether Nonionic. Ethylene oxide-alkyl phenol condensate D0. Primary amine Cationic. Fatty alcohol phosphate compositions Anionic. Stearamidylpropyl dimethyl fl-hydroxyethyl Cationic.

ammonium nitrate. 7 1 1 (ln Do. 22 1 Steararnidylpropyl dimcthyl fi-hydroxyethyl D o.

ammonium dihydrogen phosphate.

1 NorE.--Quaternary ammonium compounds of the kind embraced by Formula I. 7

which is otherwise unsubstituted, unsubstituted alkenyl having from 1 to 18 carbon atoms, inclusive, and phenylalkyl having from 1 to 4 carbon atoms, inclusive, in the alkyl portion thereof; and Y is an acidic anion selected from the group consisting of chloride, bromide, fluoride, iodide, sulfate, sulfonate, phosphate, borate, cyanide, carbonate, hydrocarbonate, thiocyanate, isocyanate, sulfite, bisulfite, nitrate, nitrite, oxalate, silicate, sulfide, cyanate and acetate.

2. The method of promoting crystal growth of 2- aminopyrimidine bisulfite obtained by acidifying with a mineral acid a mother liquor containing in aqueous solution 2-aminopyrimidine and ammonium sulfite, said method comprising adding to the said mother liquor prior to acidification thereof at least about 0.1% of the dry weight of the aforesaid 2-aminopyrimidine bisulfite of a crystalgrowth promoter comprising a quaternary ammonium compound of the formula RIII wherein Ris a substituent selected from the group consisting of abietyl and aliphatic hydrocarbon having from 7 to 18 carbon atoms, inclusive, and wherein any unsaturation between adjacent carbon atoms is a double bond; R and R" each is a substituent selected from the group consisting of unsubstituted alkyl having from 1 to 5 carbon atoms, inclusive, and hydroxy-substituted alkyl having from 1 to 5 carbon atoms, inclusive, and which is otherwise unsubstituted; R is a substitutent selected from the group consisting of unsubstituted alkyl having from 1 to 18 carbon atoms, inclusive, hydroxy-substituted alkyl having from 1 to 18 carbon atoms, inclusive, and which is otherwise unsubstituted, unsubstituted alkenyl having from 1 to 18 carbon atoms, inclusive, and phenylalkyl having from 1 to 4 carbon atoms, inclusive, in the alkyl portion thereof; and Y is an acidic anion selected from the group consisting of chloride, bromide, fluoride, iodide, sulfate, sulfonate, phosphate, borate, cyanide, carbonate, hydrocarbonate, thiocyanate, isocyanate, sulfite, bisulfite, nitrate, nitrite, oxalate, silicate, sulfide, cyanate and acetate.

3. The method as in claim 1 wherein the quaternary ammonium compound is the compound of the formula CH2CH2OH wherein Y is an acidic anion selected from the group consisting of chloride, bromide, fluoride, iodide, sulfate, suldonate, phosphate, bar-ate, cyanide, carbonate, hydrocarbonate, thiocyanaite, isocyanate, suliite, bisul-fite, nitrate, nitrite, oxalate, silicate, sulfide, cyanate and acetate.

4. The method which comprises adding to a solution containing a crystallizable organic material selected from the group consisting of 2am-inopyr-imidine bisultite, ferrous calcium citrate and acetylsultanilyl chloride at least about 0.1% by weight, based on the dry weight of the said crystallizable organic material, of a quaternary ammonium compound of the formula wherein R is a substituent selected from the group consis=ting oi abietyl and aliphatic hydrocarbon having from 7 to 18 carbon atoms, inclusive, and wherein any unsaturation between adjacent carbon atoms is a double bond; R and R" each is a substituent selected from the group consisting of unsubstituted alkyl having from 1 to 5 carbon atoms, inclusive, and hydroxyasubstituted alkyl having [from 1 to 5 carbon atoms, inclusive, and which is otherwise unsubstituted; R is a substituent selected from the group consisting of unsubstituted alkyl having from 1 to 18 carbon atoms, inclusive, hydroxy-substituted alkyl having from 1 to 18 carbon atoms, inclusive, and which is otherwise unsubstituted, unsubstituted alkenyi having from 1 to 18 carbon atoms, inclusive, and phenylalkyl having ir-om 1 to 4 carbon atoms, inclusive, in the alkyl portion thereof; and Y is an acidic anion selected from the group consisting of chloride, bromide, fluoride, iodide, sulfate, sulfionate, phosphate, borate, cyanide, carbonate, hyd=ro carbonate, thiocyanate, isocyanate, sulfite, bisulfite, nitrate, nitriate, oxalate, silicate, sulfide, cyanate and acetate, said quaternary ammonium compound promoting the crystalgrowth of said crystal-lizable organic material; crystallizid ing the said crystall-izaible organic material from the solution containing both said organic material and said qua-ternary ammonium compound; and separating the resulting crystalline material from the said solution.

5. A method as in claim 4 wherein the quaternary ammonium compound is a stearamidopropyl dimethyl p-hydroxyethyl ammonium salt of the formula given in claim 17.

-6. A method as in claim 5 wherein the stearamidopropyl dimethyl ,shydroxyethyl ammonium salt is stearamidopropyl dimethyl ,B-hydroxyethyl ammonium nitrate.

7. A method as in claim 5 wherein the stearamidopropyl dimethyl fi-hyd-roxyethyl ammonium salt is stearamidopropyl dimethyl fi-hydroxyetihyl ammonium phosphate.

8. A method as in claim 4 wherein the amount of the quaternary ammonium compound which is added to the solution of the crystallizable organic material is, by weight, irom about 0.2% to about 5% of the dry weight of the said crystallizable organic material.

9. A method as in claim 4 wherein the crystallizable organic material is Z-amino-pyrimidine bisulfite.

10. A method as in claim 4 wherein the crystallizable organic material is ferrous calcium citrate.

1:1. A method as in claim 4 wherein the crystallizable organic material is acetylsulfan-ilyl chloride.

12. In .a process of removing lby filtration, crystalline particles of 2-aminopyrimidine bisul-fite from an aqueous solution containing said particles, said ibisulfite being obtained by acidifying with a mineral acid a mother liquor containing in solution Q-aminopyrimidine and ammonium sulfite, the improvement which comprises adding stearamidop-ropyl dimethyl B-hydroxyethyl ammonium nitrate to the said mother liquor prior to acidification thereof, the amount of the said stearamidopropyl dimethyl fi hydroxyethyl ammonium nitrate which is added to the said mother liquor being, .by weight, at least 0. 1% of the dry weight of the amount of Q-aminopyrimidine bisulfite formed upon acidification of the aforesaid mother liquor containing Z-aminopyrim-idine and ammonium sulfite.

13. in a process of removing by filtration crystalline particles of Z-aminopyrimidine lbisulfite from an aqueous solution containing said particles, said bisulfi-te being obtained by acidifying with a mineral acid a mother liquor containing in solution Z-aminopyrimidine and ammonium sulfiite, the improvement which comprises ladding stearamidopropyl dimethyl n-hydroxyethyl ammonium phosphate to the said mother liquor prior to acidification thereof, the amount of the said stearamidopropyl dimethyl S-hydroxyet-hyl ammonium phosphate which is added to the said motor liquor being, by weight, at least 0 .1% of the dry weight of the amount of Z-aminOpyrimidine bisulfite tormed upon acidification of the aforesaid mother liquor containing Q-aminopyrimidine and ammonium sulfite.

Reierences Cited by the Examiner Van Hook, Crystallization: Theory and Practice (New York, 19 61), pages 204-6.

IRVING MARCUS, Primary Examiner.

H. l. LIDOFF, D. MCCUTCHEN, Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,180,870 April 27, 1965 Penn F. Spitzer, Jr. et al I It is hereby certified that err ent requiring correction and that th corrected below.

or appears in the above numbered pate said Letters Patent should read as Column 1, line 47, column 9, line S9, 10, line 8,

for "3-buteny" read 3-butenyl for "nitriate" read nitrite column for the claim reference numeral "17" read 3 Signed and sealed this 28th day of September 1965.

(SEAL) Atlest:

ERNEST W. SWIDER EDWARD J. BRENNER Atlesting Officer Commissioner of Patents 

1. THE METHOD OF PROMOTING CRYSTAL GROWTH OF A CRYSTALLIZABLE ORGANIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF 2-AMINOPYRIMIDINE BISULFITE, FERROUS CALCIUM CITRATE AND ACETYLSULFANILYL CHLORIDE, SAID METHOD COMPRISING ADDING TO A LIQUID MASS CONTAINING SAID ORGANIC MATERIAL AT LEAST ABOUT 0.1% BY WEIGHT, BASED ON THE DRY WEIGHT OF THE SAID ORGANIC MATERIAL, OF A CRYSTALGROWTH PROMOTOR COMPRISING A QUATERMARY AMMONIUM COMPOUND OF THE FORMULA 